This invention relates to portable blast cleaning devices. More particularly, it relates to a device of the type which utilizes one or more airless centrifugal blasting wheels for throwing particulate, such as steel shot, steel grit or other abrasives against a surface. Such devices are particularly adapted for cleaning large surfaces as, for example, the outside hull of a ship. The abrasive blasting process is effective for removing scales, paint chips, rust and miscellaneous debris, thereby restoring the surface in preparation for subsequent refinishing.
In previous blast heads of the type disclosed herein, it was not feasible to utilize one device to treat surfaces having different spatial orientations. For example, a ship's hull has vertically disposed portions as well as horizontal sections. Thus, a device designed to operate as an upblast cleaner could treat the horizontally disposed surfaces while a separate side blast cleaner was necessary to treat vertically disposed surfaces. Examples of these prior art devices are: U.S. Pat. No. 3,566,543 to Fogle (side blast); U.S. Pat. No. 3,788,010 to Goff (side blast); U.S. Pat. No. 3,034,262 to Paulson (side blast); copending U.S. application Ser. No. 443,389 to Diehn now U.S. Pat. No. 3,900,969 (side blast) and copending U.S. application Ser. No. 513,633 now U.S. Pat. No. 3,934,372 (upblast).
In a typical blast cleaning device, whether upblast or side blast, the device operates in sealing engagement with the surface to be treated as by a flexible seal disposed around the blast area. Usually, the seal is maintained in contact with the surface by various movable frame arrangements well known in the art. After striking the surface, the blasting particulate is reclaimed and reused in the device in order to effect economical operation.
In many of the existing devices, there exists a problem in recycling the particulate due to the contamination and buildup of foreign particles in the device. As buildup occurs, this debris from the blasting operation mixes with the abrasive and is recycled through the device, reducing its effectiveness and tending to clog or otherwise impair efficiency.
Another problem commonly experienced in devices of this type is heat buildup in the blasting area due to the dissipation of kinetic energy of the particulate against the surface being treated. A unique solution to both of these problems is the use of an air wash separator in the portable blasting head as disclosed in copending application Ser. No. 513,633. Such a design is incorporated into the present invention. The air wash separator is effective for separating material according to density, thereby permitting the heavier abrasive to pass downwardly into a recycling hopper while the lighter debris is blown out of the device. The air wash also effects cooling of the device to reduce heat buildup.
Perhaps the most serious drawback of such devices, however, is the lack of versatility due to the specialized design which each requires in order to perform efficiently. Thus, the side cleaners are incapable of performing their operation when used on a horizontally disposed surface such as the underside of a ship's hull. For example, the Paulson device operates on a gravity rebound principal, and when that device is rotated 90.degree. from its correct operating position, it will no longer function properly.
It is accordingly an object of the present invention to provide an abrasive cleaning device which recycles spent abrasive for reuse.
It is another object of the present invention to provide a portable blast cleaning head which prevents buildup of foreign matter in the returned abrasive to prevent gumming and sticking of the apparatus.
It is another object of the present invention to provide an air flow in the blast area of the device to prevent a heat buildup.
It is a further object of the present invention to provide directly in the blast head a compact and efficient means of air wash separating debris and foreign material from the abrasive.
It is another object of the present invention to provide a portable blast cleaning unit which is capable of cleaning both horizontally and vertically disposed surfaces.
It is a further object of the present invention to provide a portable blast cleaning unit which is in modular form, so that by substituting one module for another, the device is adapted to clean vertical and horizontally disposed surfaces.
Other objects and advantages of the invention will be apparent from the concluding portion of the specification.